Spearmint flavors are widely used in food, confectionary, oral care, cosmetics, and pharmaceutical products. Commonly, natural spearmint oils are used to achieve the desirable rich and natural spearmint flavor. Alternatively, complex mixtures of natural and synthetic ingredients or only synthetic ingredients can be used to create the spearmint flavor.
Natural spearmint oils are available in the marketplace. However, their production volume, composition, and price significantly vary depending on area planted, weather conditions, oil yield, and other factors. Natural oils cannot satisfy the demand for spearmint flavors and are relatively expensive. The only readily available synthetic ingredient with spearmint flavor is l-carvone. While l-carvone represents about 60-75% of spearmint oil, it doesn't provide the distinct odor and flavor of the natural spearmint oil, which in addition to l-carvone contains carveol (0.4-0.7%), carvyl acetate (1-2%), dihydrocarveol (0.1-0.2%), and dihydrocarvyl acetate (0.3-0.4%) among many other components. The synthetic versions of these compounds are offered commercially. However, their use is limited due to high prices reaching a few hundred dollars per kilogram.
Preparation of synthetic spearmint ingredient such and carveol, carvyl acetate, dihydrocarveol, and dihydrocarvyl acetate involves a few chemical steps and special catalysts and reagents. Some commonly used synthetic approaches are shown on Scheme 1.
Thus, preparation of carvyl acetate involves two chemical steps, one of which requires a large amount of the aluminum alkoxide catalyst and an excess of an auxiliary alcohol. This process generates a large amount of organic waste and highly contaminated wastewater. Furthermore, the preparation of d-dihydrocarvyl acetate is a three step chemical process. It starts with a selective hydrogenation of l-carvone to d-dihydrocarvone, which requires a specially prepared cobalt complex catalyst. The rest of the process possesses the same disadvantages as the l-carvyl acetate process.
These two components, l-carvyl acetate and d-dihydrocarvyl acetate, are essential for creating the distinct spearmint flavor. However, due to the complex technology and high prices they can't be extensively used in flavor applications. Therefore, development of a commercially viable, economical, and green process for the preparation of these compounds or their mixtures is essential for satisfying the needs of flavor industry.
It should be understood that the various embodiments are not limited to the arrangements and instrumentality shown in the drawings.